Scientific Electronic Archives (Sep 2016)
Establishment of DRIS indices and foliar nutrient levels for corn plants fertilized with various nitrogen doses and source materials associated with marine alga Lithothamnium
Abstract
The objective of this study was to evaluate leaf nutrient status and to establish the rules of the diagnosis and recommendation integrated system (DRIS) in corn for different nitrogen doses and source materials associated with Lithothamnium. The experiment was carried out from December 2010 to February 2012 in Uberlândia, Minas Gerais. The experimental design was randomized blocks with split-split plots. The main plot treatments were nitrogen source materials (immediate release and controlled-release urea), the subplot treatments were doses of 60, 100 and 120 kg of N ha-1 and control (without N application), and the sub-sub plots were treatments with or without the use of Lithothamnium. The dose of Lithothamnium corresponded to 20% of the dose of urea. Calculations to establish the diagnosis and recommendation integrated system (DRIS) were made during the experiment. In the high-yield population the treatments with the highest nitrogen dose provided the highest grain yield. The use of the controlled-release source ensured greater nutritional balance of plants. No effect of Lithothamnium on improving the efficiency of urea applied via topdressing in corn was observed. According to the DRIS indices, in the high-yield population the nutrients showed deficiencies in the following descending order: Mg>Fe>Zn>S>B>Mn>P>Cu>Ca>K>N and excess: B>S>Fe>Ca>K>Zn>Mn>Cu>Mg>P>N. The low-yield population followed the following order: Mg>Fe>Zn>Mn>Cu>N>B>P>S> Ca and excess: Zn>S>Cu>Mn>Ca>K> P>B>N>Mg>Fe.
